The present invention relates to casting machinery, and more particularly to a device useful in casting and curing plastic in the manufacture of decorative emblems.
Decorative emblems may be produced in which a foil substrate of metalized Mylar polyester film, vinyl or paper, or thin aluminum is coated with a clear plastic material. A sheet of substrate material may be prepared by screening a plurality of decorative emblems on one side of the sheet, embossing, and applying a layer of adhesive on its opposite side. A release paper is placed over the adhesive-coated side of the substrate material. A kiss cut die operation may then be used to cut through the substrate around each of the printed emblem designs without cutting the release paper. The excess substrate material between the emblems is then peeled from the release paper and discarded. Alternative methods of substrate preparation may be used. The general objective is the same, however -- to produce a sheet of release paper upon which a plurality of printed emblems are adhesively mounted.
The sheet of release paper, upon which are positioned a number of printed emblem substrates which have been embossed, is then ready for a casting operation in which a precise amount of plastic material is deposited on the upper surface of each emblem substrate. As the plastic material is placed upon each substrate, it will spread uniformly over the surface of the substrate. Because of the surface tension of the plastic, however, it will not flow off of the substrate, but will create a lense effect in that it will be slightly thicker at the center than at the edges. The plastic is then cured, resulting in an attractive decorative emblem.
It is important during the casting process that each of the foil substrates be held substantially flat. If this is not done, a portion of the fluid plastic will flow off of the substrate and the emblem will thus be ruined. Additionally the substrate must be held flat during the curing process. Since curing of the plastic will typically involve irradiation with a source of ultraviolet or infrared radiation, as well as the application of heat, dimensional changes in the sheet of release paper or the substrate, or both, may tend to warp the substrate slightly. Even if this occurs after the plastic is cured sufficiently such that it will not flow off of the surface of the substrate, the resulting emblem will be distorted in shape and, therefore, probably not acceptable.
Depending on the type of substrate used and the size of the emblem desired, it may be necessary or desirable to heat the substrates prior to casting so that the viscosity of the plastic material cast on the substrates will be reduced, thus permitting flow over larger areas. Additionally, it is desirable to be able to control the temperature of the substrates while the emblems are being irradiated with infrared or ultraviolet radiation and the plastic is undergoing a curing reaction. The sheet of release paper and emblem substrates must be held substantially flat during the entire casting and curing process. Thus it is desirable that the casting and curing apparatus be movable into operative positions rather than moving the sheet of release paper and emblems.
Ventilation must be provided during the casting and curing process. Additionally, it may be desirable, under certain circumstances, to be able to apply radiation to the plastic material only periodically during the curing process.
Thus a need exists for a device which will hold a substrate in position during casting and curing and which will control the application of radiation and the temperature of the substrates during the entire process. Such a device should be well ventilated and should permit the sequence of machine steps to be altered, depending on the type of casting operation.